A Los Alamos National Laboratory research team has examined the interface between strontium titanium trioxide (SrTiO3) and magnesium oxide (MgO) using simulations that explicitly account for the position of each atom within the nanocomposite. Their research newly demonstrated a strong dependence on the placement of elements in nanocomposites that affect various properties of the material.
Nanocomposite oxide ceramics have potential uses as ferroelectrics, fast ion conductors, nuclear fuels and for storing nuclear waste. These capabilities have generated significant interest in improving the basic properties of the material, such as the thermal conductivity. Thermal conductivity dictates how efficiently energy can be extracted from nuclear fuels.
SrTiO3 contains alternating planes of SrO and TiO2, allowing for a choice as to which layer is in contact with another material. The simulations revealed that SrO- and TiO2-terminated interfaces exhibit different atomic structures. These structures, characterized by so-called “misfit dislocations” that form when the two materials do not exactly match in size, dictate the functional properties of the interface, such as the conductivity.
The relationship between the termination chemistry and the dislocation structure of the interface offers potential avenues for tailoring transport properties and radiation damage resistance of oxide nanocomposites by controlling the termination chemistry at the interface. This could lead to new functional materials in a number of technological areas. “We believe that this discovery, that the interface structure is sensitive to the chemistry of the interface, will open the door for new research directions in oxide nanocomposites,” said Blas Uberuaga, lead researcher on the effort.
“The interfaces separating the different crystalline regions determine the transport, electrical, and radiation properties of the material as a whole,” said Pratik Dholabhai, the principal Los Alamos National Laboratory researcher on the project. “It is in the chemical makeup of these interfaces where we can improve features such as tolerance against radiation damage and fast ion conduction.”